Being federally legal is a very good policy in my opinion, anything less and you join the patchwork of tiny islands each with their own regulations. instead of the "american market" you get the "iowa market" and so on. There are many more opportunities when dealing with the country as a whole rather than individual populations carved out of the whole.
a president can not make it federally legal... it will have to go thru the senate and the house to make it legal then the president can sign it into law.....